I, Frank Seth Gaunce, have invented a system to prevent potable water distribution systems from corrosion by the protective concentration of disinfecting chemicals intentionally left in the potable water to protect its purity during delivery to point of use. Typically, the distribution systems are comprised of an iron main and distribution laterals of lead or copper, to point of use. This system is usually grounded to the electrical ground, as a safety measure, to prevent electrical shock of users.
The disinfecting chemicals (disinfectants) will corrode all three metals of the individual distribution systems even at the low protective concentrations (<1 to 4 PPMs) of the disinfectants. The metals are corroded in the order: iron, zinc, copper, which is the order of their reduction potentials. So long as the lead and copper are in contact with the iron main they are not corroded. They are not protected from corrosion by the disinfectant, electro-chemically, when iron is corroded away. When the iron is corroded away or removed, the lead and copper are next corroded. With the lead pipes, the corrosion is evidenced by the increased content of lead in the delivered water. In the case of copper, the corrosion tends to be very local, resulting in pipe pinhole corrosion leaks. For safety reasons, the metal components of the potable water system, and the iron components of the national infrastructure are typically grounded to the national grounding electrical grid matrix, which is ubiquitous wherever electricity is used. As a consequence, the potential of the potable system and the iron infrastructure are at the same potential as the electrical grid's copper grounding system which is an integral part of the electrical system.
It is recognized that the potable water supply infrastructure is electrically conductively integrated nationally, and already loosely integrated with the AC national electric grid. The grounding systems are already electrically interconnected and will assure the long-term protection of the potable water delivery systems, including those containing lead pipes. It is also recognized that corrosion of the protected lead pipes will not add lead to the potable water in quantities in excess of EPA standards. The NEARNEST equation predicts that at the zinc reduction potential and the protective concentration of disinfecting chemicals, the equilibrium concentration of lead in the potable water will be several multiples less then EPA's recommendations.
The chemical reactions with the disinfectants and the interior of metal pipes are redox reactions, which are electrolytically self-contained. That is, the reactants share electrons to produce reaction products without creating a shortage of, or an excess of electrons. The reactions go towards the lowest net energy state of the reactants and, hence, the direction of the reaction is controlled by the potential of the reactants. For corrosion prevention, the potential of the reactions is controlled in cathode mode by a sacrificial potential anode or other energy source, such as by an AC/DC transformer rectifier, supplied from the AC power supply. Preferably, the reaction potential will be from the electrical grounding systems, whose potential is raised to the reduction potential of zinc. Currently, the iron-based infrastructure is connected to the electrical grounding system which is at the grounded potential of copper, +0.521 volts, relative to a hydrogen electrode. Changing the grounding electrode from copper to zinc, changes the potential of the null point of the electrical grid from the half-cell reduction potential of copper, ++0.521 volts, to −0.76 volts, the reduction potential of zinc. These voltages are relative to a standard hydrogen electrode. A typical volt meter is scaled to zero volts at the copper grounding electrode potential of the national electrical grid.
When applying my patent, the copper grounding electrodes of the electric grid may stay in place to max-imize the safety of electrical operations personnel. The electric voltage unit, (Pe) can be changed to the thermodynamic voltage unit, (Te) by the following equations:Te=(Pe×1.12)+0.521Pe=(Te−0.521)×1/1.121 v·Te=1.51 v Pe
The redox reactions between the participating metals and the disinfectant chemicals are as follows:
1. IronFe+HClO═FeCl2+FeO+H2O                (Balanced)2Fe+2HClO═FeCl2+FeCl2+H2O        
2. LeadPb+HClO═PbCl2+PbO+H2O                (Balanced)2Pb+2HClO═PbCl2+PbO+H2O        
3. CopperCu+2HClO═CuCl+Cu2O+H2O                (Balanced)4Cu+2HClO═2CuCl+Cu2O+H2O        
These are anodic redox reactions that occur at low reduction potentials. They will proceed spontaneously and corrode the interior of the iron, lead, and copper pipes, when at an anodic oxidation reaction potential. And, they can be prevented from reacting by raising the cathodic reduction potential to the reduction potential of zinc.
Many years of unfailing service by copper and lead potable water delivery pipes connected to iron mains attest to the fact that the reduction potential of iron protects copper and lead from corrosion by potable water. Since the copper and lead are corroded by the potable water, when the iron is removed from the system, and/or disconnected, or corroded away, it can be concluded that the copper and lead pipes are protected from corrosion by the iron main.
The iron mains of the water distribution system, protect the attached copper and lead delivery pipes from corrosion by the protective concentration of disinfectant left in the potable water. Some disinfect-ant is left in the potable water to protect its purity should it be contaminated during delivery to point of use. Over decades, the iron mains fail due to corrosion and must be replaced. Currently, it is common practice to replace the iron main with a non-electrically-conducting plastic main. This removes the cathodic corrosion protection against the disinfectants. As a consequence, the lead and copper are corroded by the potable water contaminating the potable water with unacceptable amounts of lead. The copper corrosion creates the currently unexplained pinhole corrosion water leaks.
Therefore, in order to maintain and extend the life of the potable water delivery system infrastructure, it is imperative to protect the iron mains from corrosion by potable water. This patent does that by raising the reduction potential of the iron/lead and the iron/copper systems above the iron/potable water (disinfectant chemicals) redox reduction potential. Typically, this will be at the reduction potential of a zinc metal anode. At the potential of zinc metal and/or zinc metal alkali metal alloys (Zn, Al, Mg), the potable water systems are protected from corrosion by potable water. The system potential will be −1 to −2 volts relative to a copper anode, when measured with a standard volt meter, or −0.76 volts when measured relative to a standard hydrogen electrode.
Since the copper piping normally is connected to the electrical grounding system and all metal components are electrically connected; the entire system will be protected from corrosion when the electrical grid's null point is lowered to the reduction potential of a zinc anode. Zinc alloy anodes of aluminum or magnesium with high reduction potentials may also be used to protect the zinc. These may also be used to counter potential line loss. When the null point of the national electrical grid is lowered below the reduction potential of zinc, most of the national metal infrastructure less noble than zinc will be protected from corrosion.
The previous comments relate primarily to protection of the interior of the potable water distribution piping and particularly to the iron mains since the iron protects the copper and lead in the absence other protective systems. The mode of interior corrosion is by a redox reaction between the protective concentration of disinfectants and the metal pipes. In the past, this has not been recognized as a corrosion problem for lead or copper, because they were protected by the iron mains. But, currently, as failing iron mains, due to corrosion, are being replaced with non-conductive plastic, the copper and lead delivery lines are failing. My system of lowering the electrical ground grid to −1.2 volts to protect the interior and the exterior of the iron mains, also protects the interior of the copper and lead pipes, in the absence of the iron main. It also protects dedicated sacrificial anodes. Also, my system protects the exterior of the potable water system, by acting as a cathode to the cathodic corrosion protection system. Furthermore, any iron that comes in contact with the potable water delivery system, intentionally or unintentionally, is protected from electrolytic corrosion.
The cathodic corrosion protection system uses a somewhat similar chemical system as the cathodic redox approach. This system is an electro-chemical cell where, in both, a potential and an electrical current is impressed on the cathode and returned to the sacrificial anode through a common electrolyte. The sacrificial anode can also act as a potential anode for directional control of a redox reaction.
Typical cathode corrosion protection cell reactions that protect the exterior of a metal cathode by a sacrificial anode follows:Zn+Cu2O=2Cu+ZnO  (1)Zn+FeO═Fe+ZnO  (2)Zn+PbO═Pb+ZnO  (3)Zn+H2O═H2+ZnO  (4)Equations 1 through 4 are cathodic, preventing the corrosion of the metal cathode. Copper, lead, and iron are more strongly protected in the order: copper most, iron least. When all locally metal ions have been reduced, the cathodic reactions stop and the system is stagnant at the reduction potential of zinc, with the following exception: when the soil (electrolyte) is acid, water may be reduced, producing hydrogen gas at the protected metal cathode and zinc oxide at the anode, as in equation (4).
The national potable water distribution systems, the iron-based infrastructure, and the electrical grid, are a loosely integrated electrical maze. My patent not only protects lead, copper, and iron from corrosion by potable water, but it also protects the external surface of the iron infrastructure from corrosion by ozone in acid rain. It also acts as a backup for protective coatings of iron things. My corrosion prevention system can be powered from the AC electrical grid through AC/DC transformer converters or alternately by multiple zinc-based anodes. The grounding potential of the entire electrical grid grounding is lowered to −1. to −1.2 volts relative to copper ground. At this potential, all metals more noble than zinc will be protected when exposed to environmental conditions (natural conditions tend to be less aggressive than standard chemical conditions).
Implementation: The entire potable water infrastructure, and the iron-based infrastructure, are lowered to the reduction potential of zinc, by connecting a grounded zinc electrode to the AC supply ground wire. This lowers the grounding wire voltage of the AC supply system −1. to −1.2+ volts, DC. This is done at each AC stepdown transformer over the entire electrical supply grid. Because this grounding is a component of the national electrical grid, electrical power grounding is the same at all points of power use of the national iron infrastructure. Thus, because the electrical grounding system is widely used to ground infrastructure systems, the national potable water distribution system and iron infrastructure will be at the same reduction potential as zinc. Consequently, the iron mains, and iron components of the potable infrastructure, which in the past have not been protected from corrosion, will now be protected from corrosion and will continue to protect the potable water delivery system until it becomes obsolete. The unprotected iron surface of the infrastructure will also be protected from the ozone in acid rain water until the infrastructure becomes obsolete.
An option to the zinc grounding electrode is an AC/DC rectifier transformer drawing power from the AC supply. Although upgrading the grounding potential at each stepdown transformer may give adequate potential coverage, it may be desirable to install a zinc electrode or an AC/D rectifier transformer at each point of electrical use. We visualize a small AC/DC rectifier transformer unit with a DC output capacity of about 2 volts and 10 milliamps amp installed in each electrical entry service box. The necessary current potential boost will vary with the age of the infrastructure's installations. Much of the need for local grounding is fore-stalled by lowering the electrical grid grounding potential to the reduction potential of zinc. This could be done by use of AC/DC rectifier transformers at each point of electrical generation, to lower the electrical grid null point to the reduction potential of zinc.